Question

10. Junhao's sister is 5 years old. She is 36 years younger than their mother. In how
many years' time will their mother's age be 4 times her age?​

Answer 1

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GiveN:

• Junhao's sister is 5 years old.
• She is 36 years younger than their mother.

To FinD:

• In how many years' time will their mother's age be 4 times her age?

Step-by-step Explanation:

Junhao's age is 5.

Then, her mother's age = 36 + 5 = 41

Let after x years, her mother will be 4 times her age.

After x years:

• Age of Junhao = 5 + x
• Age of her mother = 41 + x

According to question,

⇒ 41 + x = 4(5 + x)

Computing the value of x,

⇒ 41 + x = 20 + 4x

⇒ 4x - x = 41 - 20

⇒ 3x = 21

⇒ x = 7 years

Quick Check:

Junhao's age will be 5 + 7 = 12. Her mother's age will be 41 + 7 = 48. Her mother's age is 4 times of Junhao✓

Thus, after 7 years Junhao's mother will be 4 times her age. And we are done! :D

Answer 2

♧GIVEN:

‐‐》Junhao's sister is 5 years

--》Mother's age is 36 + 5 = 41 years

♧SOLUTION:

--》Junaho's sister age = 5 + x----------》(1)

--》Mother's age = 41 + x------------------》(2)

♧FROM 1 AND 2

--》41 + x = 4(5 + x)

--》41 + x = 20 + 4x

--》41 - 20 = 4x - x

--》3x = 21

--》x = 21/3

--》x = 7

♧SUBSTITUTE THE VALUE OF X

--》Junaho's sister's age = 5 + 7 = 12

--》Mother's age = 41 + 7 = 48

♧HENCE PROVED...